1. Field of the Invention
The present invention relates to a controller in a volume control system and an audio output device that can control a volume via the controller.
2. Description of the Related Art
In recent years, the following reproducing form (hereinafter, referred to as a network reproducing system) is widely used. In this system, a server that saves contents, an audio output device (hereinafter, referred to as a client) and a device (hereinafter, referred to as a controller) for viewing the contents saved in the server and transmitting an instruction for reproducing the contents in the server to the client are connected to a network. When the controller is operated, the contents in the server is reproduced by the client.
In the network reproducing system, a plurality of clients is connected to the network, and the contents in the server can be reproduced from the plurality of clients by control from the controller. When the clients are audio output devices such as AV amplifiers, volumes of the respective clients can be controlled by the controller. Conventionally, the controller controls volume values of the plurality of clients according to the following method. Smallest values settable in the clients and the controller are 0, and largest values are 100.
It is assumed that a client A, a client B and a client C are connected to the network reproducing system. When volume values of the respective clients are 80, 30 and 40, respectively, an average value of the volume values of the clients is such that (80+30+40)÷3=50. The controller obtains the average value of the volumes of the clients, and stores the average value as a total volume. In the controller, when the user changes the total volume into 52, the volumes of the clients are such that 82=(80+2), 32=(30+2), and 42=(40+2), respectively.
However, when the total volume is the average value of the clients, the user cannot understand how the current volume values of the clients are close to the largest volume values settable in the clients even if a user checks the total volume. For example, even when the total volume is 50, the client A has 80% of the largest volume value (100), and the client B has 30%, and thus these values are greatly different from each other. That is to say, the user cannot directly understand positions of the volume values set for the clients with respect to the largest volume values settable in the clients even if the user checks the total volume.
Change characteristics of audio output levels (amplification degree) at a time when the volume values of the clients are different according to the clients. Further, the largest volume values settable in the clients are not always limited to 100. Therefore, when an increase in the total volume is transmitted to the clients according to the above method and when the clients change the volume values, a level of the rises in the volume varies according to the clients. FIG. 14 illustrates change characteristics of the output levels of the clients A and B. In FIG. 14, a horizontal axis represents the volume values visually recognized by the user on a display section, and a vertical axis represents output values (dB). That is to say, the values in the horizontal axis are transmitted from the controller when the total volume is changed. The largest value of the volume of the client A in FIG. 14 is 100, and the largest value of the volume of the client B is 80. When the volume values of the clients A and B are set to 100 and 80, respectively, an audio signal with the maximum output of 20 dB is output. As is clear from FIG. 14, a percentage of rise in the volume value varies according to the clients. Therefore, for example, when the volume value is changed from 40 into 50 by the control of the controller, since a degree of the rise of the output level of the client B (δB) is larger than a degree of the rise (δA) of the output level of the client A, the user feels acoustic discomfort. In general, the change characteristics of the output levels in FIG. 14 are expressed by curved lines.
The following problem further arises. When the total volume of the controllers is changed while powers of some of the plurality of clients are being set to off, the clients whose power is off cannot receive an instruction for changing the volume values, and the volume values of the clients whose power is set to off are not reflected in the total volume. Further, when the controller is powered off, the volume values of the clients are controlled and then the controller is powered on, the total volume retained in the controller does not obtain a value in which the volume values of the clients are reflected.
U.S. Pat. No. 7,571,014B1 describes that the volume values of the plurality of clients are controlled from the controller.
However, according to the above technique, the average value of the volume values of the clients is used as a volume of the group. For this reason, when the group volume is controlled, a change rate of the volumes of the clients varies.
Japanese Patent Application Laid-Open No. 2011-142601 describes that a volume value of an audio adjusting device is set based on the control of the controller.
However, according to the above technique, this document does not describe that the volume values of the plurality of clients are changed from the controller according to output levels of the clients.